1. Field of the Invention
The present invention relates to a focus detection apparatus which detects the focusing status of a photographic lens with respect to an object within multiple zones of a picture to be photographed.
2. Description of the Prior Art
In the prior art, an apparatus is known wherein a zone of an image in the center of a picture to be photographed is separated into an image pair onto line sensors, and the focusing status of the lens is detected according to an output difference of these sensors, as described in Japanese Laid-Open Publication No. SHO 59-126517.
This conventional apparatus however can detect only the focusing status of a lens with respect to an object in the center of the picture, and a focus lock method has to be used for objects on a periphery.
Japanese Laid-Open Publications Nos. HEI 1-15308 and HEI 2-58012 disclose apparatuses wherein multiple focal point detecting zones are provided in a focal plane, and multiple images in these zones are separated on multiple line sensors.
It is desirable, to reduce the effect of vignetting of the photographic lens, that the detection zones on the periphery of the focal plane are arranged in the sagittal direction perpendicular to a radial direction of the photographic lens. On the other hand, if the sensors in the reimaging plane can be arranged in a straight line, it is then possible to employ only one sensor divided into multiple parts. There are therefore different requirements regarding the arrangement of detection zones and sensors. In the prior art, however, these positional relationships were set and could not be changed.